The invention relates to centrifugal pumps in general, and more particularly to improvements in guide means for the flow of a fluid medium from the inlet to the outlet of a centrifugal pump. Still more particularly, the invention relates to improvements in guide means for the flow of a fluid medium from the exit end of the impeller to the outlet of a centrifugal pump.
German Auslegeschrift No. 22 57 949 discloses a centrifuqal pump with a mixed flow impeller and an energy converting guide wheel which is located at the exit end of the impeller and serves to direct the flow of fluid into an elbow which, in turn, directs the fluid into a radially outwardly extending discharge branch of the outer casing of the pump. The fluid medium must flow through the guide wheel and is thereupon caused to flow through an inner casing which is installed in the outer casing and is provided with one or more bearings for the pump shaft. The efficiency of the pump is unsatisfactory due to the aforedescribed guidance of the fluid, and the initial cost is high.
Austrian Pat. No. 347 268 discloses a pump with an axial or mixed flow impeller. The outer casing of the pump is provided with an inlet in the form of a suction branch and with an outlet in the form of a radially disposed discharge branch. The outer casing confines an inner casing which rotatably carries a shaft for the impeller. The inner casing is called a supporting tube and its outer diameter increases gradually from the exit end of the impeller to the discharge branch. The patented pump further comprises a deflecting shield which is disposed between the inner and outer casings and cooperates with channels in the internal surface of the outer casing to direct the fluid flow toward the discharge branch. The deflecting shield is provided with a wedge which is located opposite the discharge branch of the outer casing. The fluid stream which issues from the impeller is oriented by the deflecting shield and flows through the space between the inner and outer casings in substantial parallelism with the axis of the pump shaft. The aforementioned wedge serves to divide the fluid stream into two branches which flow along the exterior of the inner casing and toward the discharge branch. In order to reduce losses, the outer casing is provided with two additional channels which are formed in its internal surface opposite the discharge branch. These channels contribute to the cost of the outer casing and of the entire centrifugal pump. Furthermore, the shield contributes unduly to the axial length of the pump.
Published German patent application No. 22 31 128 discloses a spherical housing for use in reactor pumps. The fluid-admitting and fluid-discharging chambers are disposed in one and the same casing. Flow guiding elements are installed in the fluid admitting portion of the spherical housing, and similar flow guiding elements are installed in the fluid discharging portion. The housing of this pump is complex and expensive.